BOLOGNA To this day, the causes of both the vocal decline and eventual death of legendary soprano Maria Callas have remained a mystery. Several hypotheses have surrounded the Sep. 1977 death at the singer’s Paris home, including suicide, which in recent years has been strongly disputed by her family.

Now a new detailed scientific study by Italian vocal researchers, Franco Fussi and Nico Paolillo, that relies on medical records and the latest audio technology, may shed further light on the truth of her demise.

The great soprano was suffering from dermatomyositis, a disease that causes a failure of the muscles and tissues, including the larynx, and a noticeable decline in Callas’ vocal chords began to afflict her as early as the 1960s. Treatment for dermatomyositis includes corticosteroids and immunosuppressive agents, which over the long term can cause heart failure. Thus the official cause of death, cardiac arrest, which many had previously considered a cover-up for suicide, now has hard scientific evidence behind it, say Fussi and Paolillo.

The pair presented their findings last week to a roundtable of experts at the University of Bologna, in an event hosted by Il Saggiatore Musicale, a cultural quarterly. The starting point of the study — through the use of modern audio technology — was to document when and how her voice changed over time. They analyzed live Callas studio recordings to ascertain the evolution her voice from the 1950’s through to the 1970’s, when her voice began to show increasing problems of transition and uneven performances.

Recordings of the same songs in different years were subjected to spectrographic analysis, which revealed that during the last years the soprano Maria Callas had become a mezzo-soprano: characterized by an inability to hit the high notes well.

But Fussi — a well-known specialist in Phoniatrycs and Otolaryngology– and Paolillo say the last recorded videos of Callas clearly show muscle failure. In the waning years her chest did not fully expand to its full capacity, leaving her with poor posture and, perhaps above all, a strong contraction of her deltoid muscles, which rendered far less capable of hitting certain notes.

In 1975 the physician Mario Giacovazzo visited the singer and determined that she suffered from dermatomyositis but only revealed the secret in 2002. Fussi and Paolillo looked deeper into the clinical picture of disease, which carried to its extreme can cause cardiac arrest.

Their findings could help rule out the hypotheses that the cause of death of this 20th century icon was either barbiturates or depression linked to her failed relationship with Aristotle Onassis. Married to the industrialist Giovanni Battista Meneghini, Callas had an affair with the Greek shipping magnate in the summer of 1959. Unconfirmed reports held that Callas and Onassis had a child, who died shortly after birth. Callas separated from Meneghini, but was then subsequently abandoned by Onassis, who would eventually marry Jacqueline Kennedy in 1968.

Health issues and apparent emotional turmoil had long followed the career of the US-born Greek singer. In 1954, Callas dramatically lost 65 pounds, sparking rumors that she had swallowed Taenia solium — a tapeworm. Fussi and Paolillo note that such dramatic weight loss is now known to reduce physical support of the vocal chords and hamper homogeneity of the tonal registers.

The research may also help explain the infamous Jan. 1958 evening when Callas abruptly stopped during the first act in Bellini's Norma at the Rome Opera. The scene prompted Italy’s President of the Republic Giovanni Gronchi to leave after the first act, and Callas was widely criticized for her diva-like ways. But by applying spectrographic analysis to that stock footage, which has been restored after being damaged for years, the researchers say they now have a clearer picture. Fussi and Paolillo found a tired voice, unequal in the various registers, without the control once displayed. It was not a diva’s whim that caused her to abruptly stop the show. Callas was not well, tracheitis had set in, and her muscles were probably already giving way. The decline had begun.